Over the last decade, the amount of information that is conveyed electronically has increased dramatically. As the need for greater communications bandwidth increases, the importance of efficient use of communications infrastructure increases as well. The emergence of dense-wavelength division multiplexing (DWDM) technology has improved the bandwidth problem by increasing the capacity of an optical fiber. In wavelength division multiplexing (WDM), channels are arranged by a predetermined wavelength interval, and signals are loaded on each channel. Also, a number of channels are optically multiplexed, and the signals are transmitted through an optical fiber. A receiver optically demultiplexes the channels according to their wavelengths and utilizes each channel separately. DWDM is now well established as a principal technology to enable large transport capacities in long-haul communications.
However, the increased capacity creates a serious mismatch with current electronic switching technologies that are designed to process individual channels within a DWDM link. In electronic switching, the optical fiber additionally requires a photoelectric converter for converting an optical signal into an electrical signal and an electro-optic converter for converting an electrical signal into an optical signal, which results in an increased cost. While electronic switching routers, such as internet protocol (IP) routers, can be used to switch data using the individual channels within a fiber, this approach implies that tens or hundreds of switch interfaces must be used to terminate a single DWDM fiber with a large number of channels. This could lead to a significant loss of statistical multiplexing efficiency when the parallel channels are used simply as a collection of independent links, rather than as a shared resource.
In order to solve such problems, there were several proposed solutions in the related art optical switching technologies, which do not convert the transferred optical signal into the electrical signal but processes the optical signal directly. Optical switching technologies based on wavelength routing (circuit-switching) of a limited pool of wavelengths don't make efficient use of the transmission medium when data traffic dominates the public network. This is the case today where the increasing demand for bandwidth is largely due to a spectacular growth in IP data traffic. All-optical packet switching would be an optimum transfer mode to handle the flood of optical IP packets to and from the Internet core in the most efficient way. However, a number of packet-switching operations (e.g. ultra fast pulsing, bit and packet synchronization, ultra-high-speed switching, buffering and header processing) cannot be performed optically, on a packet-by-packet basis today.
An optical burst switching (OBS) network makes use of both optical and electronic technologies. The electronics provides control of system resources by assigning individual user data bursts to channels of a DWDM fiber, while optical technology is used to switch the user data channels entirely in the optical domain. In the OBS, the length of a data packet can be variable and packet routing can be performed without an optical buffer by setting a path in advance using a control packet.
In the OBS network, generally, Internet protocol (IP) packets or data stream of any form inputted in an optical domain are gathered as a data burst in an edge node, and such data bursts are routed by way of a core node depending on their destinations or Quality of Services (QoS) and then sent to the destination nodes. Further, a burst header packet and the data burst are respectively transmitted on different channels and at an offset time. That is, the burst header packet is transmitted earlier than the data burst by the offset time and it reserves a optical path through which the data burst is transferred, so that the data burst can be transmitted through the optical network at a high speed without being buffered.
However, in the OBS network, data burst can be lost due to a contention in the optical switch. One optical burst switching scheme uses wavelength conversion to reduce the contention on output channels. Unfortunately, all optical wavelength converters may remain expensive now and in foreseeable future. The need for wavelength converter makes the cost of deploying OBS networks high.
In order to remove the wavelength conversion constraints in OBS networks, Time Sliced Optical Burst Switching (TSOBS) replaces switching in the wavelength domain with switching in the time domain. However, although the TSOBS router eliminates the wavelength converters, it uses more optical crossbars than a traditional OBS router, and also makes extensive use of fiber delay lines (FDLs) which are not required for traditional OBS routers. In addition, synchronizing time slots also presents a challenge.
Therefore, it is desirable to provide optical switching methods and systems providing multi-wavelength switching without wavelength conversion. The methods and systems discussed herein provide a lower cost option for fiber optic switching.